The present invention relates to an improvement of a head base drive mechanism in a tape player for bringing the head into contact with a cassette tape held in a cassette receiving chamber during the recording and playback operations and for moving the head away from the tape during fast forwarding and rewinding operations or during the tape stop.
Heretofore, as a head base drive mechanism of this type, there has been known such a device as shown in FIGS. 1 to 4.
Such a conventional device will now be explained with reference to those figures. The numeral 1 denotes a trigger plunger attached to a chassis A, the trigger plunger 1 being connected to one end of a trigger lever 3 which is supported pivotably by a shaft 2 on the chassis A.
The numeral 4 denotes a capstan shaft mounted to the chassis. On said capstan shaft is fixedly mounted a flywheel 5. The flywheel 5 is adapted to be rotated by a belt 8 which is stretched between a motor pulley 7 mounted on a shaft of a motor 6 and the flywheel 5. On the capstan shaft 4 is also coaxially fixed a capstan gear 9.
The numeral 10 denotes a cam gear in the form of a rotor adapted to engage the capstan gear 9. Said cam gear 10 is mounted to said chassis A to come into mesh engagement with said capstan gear and has two notched sections 10a and 10b therearound. Said cam gear 10 is further provided with a cam 11 and a pin 12 thereon. Said cam 11 is of a generally oval shape having a substantially large diameter section and a substantially smallest diameter section and is fixed to the cam gear on a head-base-stop side of the drive pin which will be explained later.
The numeral 14 denotes a trigger spring anchored at one end thereof to the chassis A. When the notched section 10a of the cam gear 10 moves to the position to face the capstan gear 9, the cam gear 10 takes a first position as shown in FIG. 1. In this position, the rotation of the flywheel 5 is adapted to be transmitted to the cam gear 10 since the pin 12 in contact with the trigger spring 14 is urged by the latter to rotate the cam gear 10 in the arrow-marked direction.
Likewise, when the notched section 10b is in the position to face the capstan gear 9, the cam gear 10 takes a second position as shown in FIG. 3. In this position, the pin 12 comes into contact with the trigger spring 14 to receive the force to further rotate the cam gear 10 in the arrow-marked direction.
The numeral 15 denotes a head base equipped with a head (not shown). The head base 15 is slidably movable with respect to the chassis A between a playback position and a stop position. Said head base 15 taking the playback position is urged downward in the drawing toward the stop position by means of a head base return spring 16 which is anchored at one end thereof to the chassis A. Consequently, the head moves away from the tape. On the head base 15 is fixedly erected a cam follower in the form of a drive pin 17 adapted to contact the cam 11.
Further, one end of a trigger lever spring 18 is anchored to the trigger lever 3 whereas the other end is fixed to the chassis. A lug 10c is formed on the cam gear 10. Where a play button (not shown) for recording and playback of the tape recorder is not operated, the trigger plunger 1 is not supplied with an electric current. Therefore, trigger lever 3 is pulled by the trigger lever spring 18 and the lug 10c of the cam gear 10 is locked by a retaining portion 3a of the trigger lever 3 at the first position as shown in FIG. 1 such that the cam gear 10 cannot rotate in the above direction.
When the play button is operated to supply an electric current through the trigger plunger 1, the trigger lever 3 pivots against the trigger lever spring 18 to bring the lug 10c of the cam gear 10 into abutment with an abutting portion 3b of the trigger lever 3 after said retaining portion 3a releases the lug 10c such that the rotation of the cam gear 10 is stopped to take the second position as shown in FIG. 3.
While the tape recorder is in neither recording nor reproducing operation, the notched section 10a of the cam gear 10 is in the position to face the capstan gear 9 and the lug 10c is retained by the retaining portion 3a of the cam lever 3, thus preventing the rotating of the cam gear 10, as shown in FIG. 1.
In this state, if the play button for recording and playback is operated, the trigger plunger 1 is supplied with an electric current and energized such that the trigger lever 3 is pulled to pivot and its retaining portion 3a is disengaged from the lug 10c. The cam gear 10 starts rotating since the pin 12 is urged in the arrow-marked direction by the trigger spring 14 as previously noted. As a result, the cam gear 10 comes into mesh engagement with the capstan gear 9 to maintain the rotation.
Since the cam 11 also rotates together with the cam gear 10 until it contacts and pushes the drive pin 17, the head base 15 is pushed toward the playback position against the head base return spring 16, thereby causing the head to contact the tape.
When the movement of the head base 15 due to the continued rotation of the cam gear 10 is finished, the notched section 10b of the cam gear 10 arrives at the position to face the capstan gear 9 as shown in FIG. 3 with the result that the rotation of the capstan gear 9 is no longer transmitted to the cam gear 10.
At this time, the pin 12 pushes the trigger spring 14 through its way onto the opposite side of its dead point. As a result, it begins to undergo the urging force in the arrow-marked direction of the cam gear 10 until the lug 10c abuts the abutting portion 3b of the trigger lever 3 to stop the rotation of the cam gear 10 such that the head is kept in contact with the tape at the playback position.
Next, when the stop button is pressed for stopping recording and playback, the supply of electric current to the trigger plunger 1 is cut off such that trigger lever 3 is pulled by the trigger lever spring 18 to pivot and disengage its abutting portion 3b from the lug 10c, as shown in FIG. 4. Consequently, the trigger spring 14 causes the pin 12 to rotate the cam gear such that the toothed portion of the cam gear 10 is brought into engagement with the capstan gear 9 to rotate the same.
When the cam 11 rotates along with the cam gear 10 in this situation, said cam 11 no longer actuates the drive pin 17, since the substantially smallest section of the cam 11 comes into facing relation with the drive pin 17. As a result, the head base 15 is brought downward in the drawing by the head base return spring 16.
Then, as the cam gear 10 continues to rotate, its notched section 10a arrives at the position to face the capstan gear 9, so that the rotation of the capstan gear 9 is no longer transmitted to the cam gear 10, and the pin 12 comes into contact with the trigger lever spring 14 and begins to undergo the urging force in the rotational direction past its bottom dead center by means of the trigger lever spring 14, whereupon the lug 10c is retained by the retaining portion 3a of the trigger lever 3 as shown in FIG. 1 again.
In this way, the tape recorder head contacts and moves away from the tape between the record/playback position and the stop position. In such a conventional device, however, it is only the force of the head base return spring 16 that actuates the head base 15 for stopping recording or playback operation. In case where the force of the head base return spring 16 is made stronger to overcome the sliding loss during the head base movement away from the tape and to cope with load of the head lead wire, increasing load due to hardened lubricating oil under low temperatures, etc., the force for actuating the head base 15 in the opposite direction for recording or playback is required to be larger. In such a design, the components are subject to wear sooner or the speed of the rotating flywheel is apt to drop.
If the force of the head base returning spring 16 is not made stronger on the other hand, the head base 15 may not go downward in the drawing in the event of an abnormal load thus making it impossible to take out the cassette from the player.